Retrieval of microphysical properties of liquid water clouds from atmospheric lidar measurements: comparison of the Raman dual field of view and the depolarization techniques

2017 ◽  
Author(s):  
Cristofer Andres Jimenez Jimenez ◽  
Jörg Schmidt ◽  
Ulla Wandinger ◽  
David Donovan ◽  
Albert Ansmann ◽  
...  
Keyword(s):  
Liquid Water ◽  
Field Of View ◽  
Microphysical Properties ◽  
Lidar Measurements

Dual-field-of-view Raman lidar measurements for the retrieval of cloud microphysical properties

2013 ◽  
Vol 52 (11) ◽  
pp. 2235 ◽  
Author(s):  
Jörg Schmidt ◽  
Ulla Wandinger ◽  
Aleksey Malinka
Keyword(s):  
Field Of View ◽  
Raman Lidar ◽  
Microphysical Properties ◽  
Lidar Measurements

scholarly journals Benefit of depolarization ratio at λ = 1064 nm for the retrieval of the aerosol microphysics from lidar measurements

2014 ◽  
Vol 7 (11) ◽  
pp. 3773-3781 ◽  
Author(s):  
J. Gasteiger ◽  
V. Freudenthaler
Keyword(s):  
Optical Properties ◽  
Mass Concentration ◽  
Volcanic Ash ◽  
Single Scattering ◽  
Depolarization Ratio ◽  
Complex Relation ◽  
Microphysical Properties ◽  
Lidar Measurements ◽  
Increased Sensitivity ◽  
Linear Depolarization Ratio

Abstract. A better quantification of aerosol properties is required for improving the modelling of aerosol effects on weather and climate. This task is methodologically demanding due to the diversity of the microphysical properties of aerosols and the complex relation between their microphysical and optical properties. Advanced lidar systems provide spatially and temporally resolved information on the aerosol optical properties that is sufficient for the retrieval of important aerosol microphysical properties. Recently, the mass concentration of transported volcanic ash, which is relevant for the flight safety of aeroplanes, was retrieved from measurements of such lidar systems in southern Germany. The relative uncertainty of the retrieved mass concentration was on the order of ±50%. The present study investigates improvements of the retrieval accuracy when the capability of measuring the linear depolarization ratio at 1064 nm is added to the lidar setup. The lidar setups under investigation are based on those of MULIS and POLIS of the Ludwig-Maximilians-Universität in Munich (Germany) which measure the linear depolarization ratio at 355 and 532 nm with high accuracy. The improvements are determined by comparing uncertainties from retrievals applied to simulated measurements of this lidar setup with uncertainties obtained when the depolarization at 1064 nm is added to this setup. The simulated measurements are based on real lidar measurements of transported Eyjafjallajökull volcano ash. It is found that additional 1064 nm depolarization measurements significantly reduce the uncertainty of the retrieved mass concentration and effective particle size. This significant improvement in accuracy is the result of the increased sensitivity of the lidar setup to larger particles. The size dependence of the depolarization does not vary strongly with refractive index, thus we expect similar benefits for the retrieval in case of measurements of other volcanic ash compositions and also for transported desert dust. For the retrieval of the single scattering albedo, which is relevant to the radiative transfer in aerosol layers, no significant improvements were found.

scholarly journals Aerosol optical and microphysical retrievals from a hybrid multiwavelength lidar data set – DISCOVER-AQ 2011

2014 ◽  
Vol 7 (9) ◽  
pp. 3095-3112 ◽  
Author(s):  
P. Sawamura ◽  
D. Müller ◽  
R. M. Hoff ◽  
C. A. Hostetler ◽  
R. A. Ferrare ◽  
...  
Keyword(s):  
Remote Sensing ◽  
In Situ Measurements ◽  
Index Of Refraction ◽  
High Spectral Resolution ◽  
Lidar Data ◽  
Data Set ◽  
Microphysical Properties ◽  
Lidar Measurements ◽  
Multiwavelength Lidar

Abstract. Retrievals of aerosol microphysical properties (effective radius, volume and surface-area concentrations) and aerosol optical properties (complex index of refraction and single-scattering albedo) were obtained from a hybrid multiwavelength lidar data set for the first time. In July 2011, in the Baltimore–Washington DC region, synergistic profiling of optical and microphysical properties of aerosols with both airborne (in situ and remote sensing) and ground-based remote sensing systems was performed during the first deployment of DISCOVER-AQ. The hybrid multiwavelength lidar data set combines ground-based elastic backscatter lidar measurements at 355 nm with airborne High-Spectral-Resolution Lidar (HSRL) measurements at 532 nm and elastic backscatter lidar measurements at 1064 nm that were obtained less than 5 km apart from each other. This was the first study in which optical and microphysical retrievals from lidar were obtained during the day and directly compared to AERONET and in situ measurements for 11 cases. Good agreement was observed between lidar and AERONET retrievals. Larger discrepancies were observed between lidar retrievals and in situ measurements obtained by the aircraft and aerosol hygroscopic effects are believed to be the main factor in such discrepancies.

scholarly journals Comparison between two lidar methods to retrieve microphysical properties of liquid-water clouds

2018 ◽  
Vol 176 ◽  
pp. 01032 ◽  
Author(s):  
Cristofer Jimenez ◽  
Albert Ansmann ◽  
David Donovan ◽  
Ronny Engelmann ◽  
Jörg Schmidt ◽  
...  
Keyword(s):  
Temporal Resolution ◽  
Liquid Water ◽  
High Temporal Resolution ◽  
Lidar System ◽  
Microphysical Properties

Since 2010, the Raman dual-FOV lidar system permits the retrieval of microphysical properties of liquid-water clouds during nighttime. A new robust lidar depolarization approach was recently introduced, which permits the retrieval of these properties as well, with high temporal resolution and during daytime. To implement this approach, the lidar system was upgraded, by adding a three channel depolarization receiver. The first preliminary retrieval results and a comparison between both methods is presented.

scholarly journals Simulation of the aerosol effect on the microphysical properties of shallow stratocumulus clouds over East Asia using a bin-based meso-scale cloud model

2010 ◽  
Vol 10 (10) ◽  
pp. 23449-23495 ◽  
Author(s):  
I.-J. Choi ◽  
T. Iguchi ◽  
S.-W. Kim ◽  
S.-C. Yoon ◽  
T. Nakajima
Keyword(s):  
East Asia ◽  
Liquid Water ◽  
Cloud Model ◽  
Atmospheric Condition ◽  
Meteorological Condition ◽  
Sensitivity Factor ◽  
Target Area ◽  
Precipitation Efficiency ◽  
Microphysical Properties ◽  
Meso Scale

Abstract. A bin-based meso-scale cloud model has been employed to explore the aerosol influence on the cloud microphysical properties and precipitation efficiency of shallow stratocumulus in East Asia in March 2005. We newly constructed aerosol size distributions and hygroscopicity parameters for five aerosol species that reproduced observed aerosol and cloud condensation nuclei (CCN) number concentrations in the target period, and thereby used in model simulation of the cloud microphysical properties and precipitation efficiency. It is found that the simulated results were satisfactorily close to the satellite-based observation. Significant effects of aerosols as well as of the meteorological condition were found in the simulated cloud properties and precipitation as confirmed by comparing maritime and polluted aerosol cases and by a sensitivity test with interchanging the aerosol conditions for two cases. Cloud droplets in the polluted condition tended to exhibit relatively narrower cloud drop spectral widths with a bias toward smaller droplet sizes than those in maritime condition, supporting the dispersion effect. The polluted aerosol condition also had a tendency of thinner and higher cloud layers than maritime aerosol condition under relatively humid meteorological condition, possibly due to enhanced updraft. In our cases, vertical structures of cloud droplet number and size were affected predominantly by the change in aerosol conditions, whereas in the structures of liquid water content and cloud fraction were influenced by both meteorological and aerosol conditions. Aerosol change made little differences in cloud liquid water, vertical cloud structure, and updraft/downdraft velocities between the maritime and polluted conditions under dry atmospheric condition. Quantitative evaluations of the sensitivity factor between aerosol and cloud parameters revealed a large sensitivity values in the target area compared to the previously reported values, indicating the strong aerosol-cloud interaction.

scholarly journals Retrieval of aerosol microphysical properties from atmospheric lidar sounding: an investigation using synthetic measurements and data from the ACEPOL campaign

2021 ◽  
Vol 14 (6) ◽  
pp. 4755-4771
Author(s):  
William G. K. McLean ◽  
Guangliang Fu ◽  
Sharon P. Burton ◽  
Otto P. Hasekamp
Keyword(s):  
Refractive Index ◽  
Effective Radius ◽  
High Spectral Resolution ◽  
Imaginary Component ◽  
The Real ◽  
Microphysical Properties ◽  
Lidar Measurements ◽  
Fine Mode ◽  
Truth Value ◽  
Real Refractive Index

Abstract. This study presents an investigation of aerosol microphysical retrievals from high spectral resolution lidar (HSRL) measurements. Firstly, retrievals are presented for synthetically generated lidar measurements, followed by an application of the retrieval algorithm to real lidar measurements. Here, we perform the investigation for an aerosol state vector that is typically used in multi-angle polarimeter (MAP) retrievals, so that the results can be interpreted in relation to a potential combination of lidar and MAP measurements. These state vectors correspond to a bimodal size distribution, where column number, effective radius, and effective variance of both modes are treated as fit parameters, alongside the complex refractive index and particle shape. The focus is primarily on a lidar configuration based on that of the High Spectral Resolution Lidar-2 (HSRL-2), which participated in the ACEPOL (Aerosol Characterization from Polarimeter and Lidar) campaign, a combined project between NASA and SRON (Netherlands Institute for Space Research). The measurement campaign took place between October and November 2017, over the western region of the USA. Six different instruments were mounted on the aeroplane: four MAPs and two lidar instruments, HSRL-2 and the Cloud Physics Lidar (CPL). Most of the flights were carried out over land, passing over scenes with a low aerosol load. One of the flights passed over a prescribed forest fire in Arizona on 9 November, with a relatively higher aerosol optical depth (AOD), and it is the data from this flight that are focussed on in this study. A retrieval of the aerosol microphysical properties of the smoke plume mixture was attempted with the data from HSRL-2 and compared with a retrieval from the MAPs carried out in previous work pertaining to the ACEPOL data. The synthetic HSRL-2 retrievals resulted for the fine mode in a mean absolute error (MAE) of 0.038 (0.025) µm for the effective radius (with a mean truth value of 0.195 µm), 0.052 (0.037) for the real refractive index, 0.010 (7.20×10-3) for the imaginary part of the refractive index, 0.109 (0.071) for the spherical fraction, and 0.054 (0.039) for the AOD at 532 nm, where the retrievals inside brackets indicate the MAE for noise-free retrievals. For the coarse mode, we find the MAE is 0.459 (0.254) µm for the effective radius (with a mean truth value of 1.970 µm), 0.085 (0.075) for the real refractive index, 2.06×10-4 (1.90×10-4) for the imaginary component, 0.120 (0.090) for the spherical fraction, and 0.051 (0.039) for the AOD. A study of the sensitivity of retrievals to the choice of prior and first guess showed that, on average, the retrieval errors increase when the prior deviates too much from the truth value. These experiments revealed that the measurements primarily contain information on the size and shape of the aerosol, along with the column number. Some information on the real component of the refractive index is also present, with the measurements providing little on absorption or on the effective variance of the aerosol distribution, as both of these were shown to depend heavily on the choice of prior. Retrievals using the HSRL-2 smoke-plume data yielded, for the fine mode, an effective radius of 0.107 µm, a real refractive index of 1.561, an imaginary component of refractive index of 0.010, a spherical fraction of 0.719, and an AOD at 532 nm of 0.505. Additionally, the single-scattering albedo (SSA) from the HSRL-2 retrievals was 0.940. Overall, these results are in good agreement with those from the Spectropolarimeter for Planetary Exploration (SPEX) and Research Scanning Polarimeter (RSP) retrievals.

scholarly journals Version 4 CALIPSO IIR ice and liquid water cloud microphysical properties, Part I: the retrieval algorithms

2020 ◽  
Author(s):  
Anne Garnier ◽  
Jacques Pelon ◽  
Nicolas Pascal ◽  
Mark A. Vaughan ◽  
Philippe Dubuisson ◽  
...  
Keyword(s):  
Liquid Water ◽  
Cloud Base ◽  
Transfer Model ◽  
Effective Diameter ◽  
Ice Clouds ◽  
Clear Sky ◽  
Brightness Temperatures ◽  
Microphysical Properties ◽  
Data Products ◽  
Level 2

Abstract. Following the release of the Version 4 Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) data products from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission, a new version 4 (V4) of the CALIPSO Imaging Infrared Radiometer (IIR) Level 2 data products has been developed. The IIR Level 2 data products include cloud effective emissivities and cloud microphysical properties such as effective diameter and ice or liquid water path estimates. Dedicated retrievals for water clouds were added in V4, taking advantage of the high sensitivity of the IIR retrieval technique to small particle sizes. This paper (Part I) describes the improvements in the V4 algorithms compared to those used in the version 3 (V3) release, while results will be presented in a companion (Part II) paper. To reduce biases at very small emissivities that were made evident in V3, the radiative transfer model used to compute clear sky brightness temperatures over oceans has been updated and tuned for the simulations using MERRA-2 data to match IIR observations in clear sky conditions. Furthermore, the clear-sky mask has been refined compared to V3 by taking advantage of additional information now available in the V4 CALIOP 5-km layer products used as an input to the IIR algorithm. After sea surface emissivity adjustments, observed and computed brightness temperatures differ by less than ± 0.2 K at night for the three IIR channels centered at 08.65, 10.6, and 12.05 µm, and inter-channel biases are reduced from several tens of Kelvin in V3 to less than 0.1 K in V4. We have also aimed at improving retrievals in ice clouds having large optical depths by refining the determination of the radiative temperature needed for emissivity computation. The initial V3 estimate, namely the cloud centroid temperature derived from CALIOP, is corrected using a parameterized function of temperature difference between cloud base and top altitudes, cloud absorption optical depth, and the CALIOP multiple scattering correction factor. As shown in Part II, this improvement reduces the low biases at large optical depths that were seen in V3, and increases the number of retrievals in dense ice clouds. As in V3, the IIR microphysical retrievals use the concept of microphysical indices applied to the pairs of IIR channels at 12.05 μm and 10.6 μm and at 12.05 μm and 08.65 μm. The V4 algorithm uses ice look-up tables (LUTs) built using two ice crystal models from the recent TAMUice 2016 database, namely the single hexagonal column model and the 8-element column aggregate model, from which bulk properties are synthesized using a gamma size distribution. Four sets of effective diameters derived from a second approach are also reported in V4. Here, the LUTs are analytical functions relating microphysical index applied to IIR channels 12.05 µm and 10.6 µm and effective diameter as derived from in situ measurements at tropical and mid-latitudes during the TC4 and SPARTICUS field experiments.

scholarly journals Lidar observation and model simulation of a volcanic-ash-induced cirrus cloud during the Eyjafjallajökull eruption

2012 ◽  
Vol 12 (6) ◽  
pp. 15675-15707 ◽  
Author(s):  
C. Rolf ◽  
M. Krämer ◽  
C. Schiller ◽  
M. Hildebrandt ◽  
M. Riese
Keyword(s):  
Volcanic Ash ◽  
Model Simulation ◽  
Cirrus Cloud ◽  
Backward Trajectories ◽  
Microphysical Properties ◽  
Ice Nuclei ◽  
A Value ◽  
Lidar Measurements ◽  
Before And After ◽  
Western Germany

Abstract. Heterogeneous ice formation induced by volcanic ash from the Eyjafjallajökull volcano eruption in April 2010 is investigated based on the combination of a cirrus cloud observed with a backscatter lidar over Jülich (Western Germany) and model simulations along backward trajectories. The microphysical properties of the cirrus cloud could only be represented by the microphysical model under the assumption of an enhanced number of efficient ice nuclei originating from the volcanic eruption. The ice nuclei (IN) concentration determined by lidar measurements directly before and after cirrus cloud occurrence implies a value of around 0.1 cm−3 (in comparison clean IN conditions: 0.01 cm−3). This leads to a cirrus cloud with rather small ice crystals having a mean radius of 12 μm and a modification of the ice particle number (0.08 cm−3 instead of 3 × 10−4 cm−3 under clean IN conditions). The effectiveness of ice nuclei was estimated by the use of the microphysical model and the backward trajectories based on ECMWF data, establishing a freezing threshold of around 105% relative humidity with respect to ice in a temperature range from −45 to −55 °C. Only with these highly efficient ice nuclei was it possible for the cirrus cloud to be formed in a slightly supersaturated environment.

scholarly journals Benefit of depolarization ratio at λ = 1064 nm for the retrieval of the aerosol microphysics from lidar measurements

2014 ◽  
Vol 7 (5) ◽  
pp. 5095-5115
Author(s):  
J. Gasteiger ◽  
V. Freudenthaler
Keyword(s):  
Optical Properties ◽  
Mass Concentration ◽  
Single Scattering ◽  
Sufficient Information ◽  
Depolarization Ratio ◽  
Aerosol Composition ◽  
Microphysical Properties ◽  
Lidar Measurements ◽  
Increased Sensitivity ◽  
Linear Depolarization Ratio

Abstract. A better quantification of aerosol microphysical and optical properties is required to improve the modelling of aerosol effects on weather and climate. This task is methodologically demanding due to the huge diversity of aerosol composition and of their shape and size distribution, and due to the complexity of the relation between the microphysical and optical properties. Lidar remote sensing is a valuable tool to gain spatially and temporally resolved information on aerosol properties. Advanced lidar systems provide sufficient information on the aerosol optical properties for the retrieval of important aerosol microphysical properties. Recently, the mass concentration of transported volcanic ash, which is relevant for the flight safety of airplanes, was retrieved from measurements of such lidar systems in Southern Germany. The relative uncertainty of the retrieved mass concentration was on the order of ±50%. The present study investigates improvements of the retrieval accuracy when the capability of measuring the linear depolarization ratio at 1064 nm is added to the lidar setup. The lidar setups under investigation are based on the setup of MULIS and POLIS of the LMU in Munich which measure the linear depolarization ratio at 355 nm and 532 nm with high accuracy. By comparing results of retrievals applied to simulated lidar measurements with and without the depolarization at 1064 nm it is found that the availability of 1064 nm depolarization measurements reduces the uncertainty of the retrieved mass concentration and effective particle size by a factor of about 2–3. This significant improvement in accuracy is the result of the increased sensitivity of the lidar setup to larger particles. However, the retrieval of the single scattering albedo, which is relevant for the radiative transfer in aerosol layers, does hardly benefit from the availability of 1064 nm depolarization measurements.

scholarly journals CADEX and beyond: Installation of a new PollyXT site in Dushanbe

2019 ◽  
Vol 99 ◽  
pp. 02010
Author(s):  
Ronny Engelmann ◽  
Julian Hofer ◽  
Abduvosit N. Makhmudov ◽  
Holger Baars ◽  
Karsten Hanbuch ◽  
...  
Keyword(s):  
Asian Dust ◽  
Raman Lidar ◽  
Technical Institute ◽  
Lidar System ◽  
Microphysical Properties ◽  
Source Regions ◽  
Central Asian ◽  
Lidar Measurements ◽  
Academy Of Sciences

During the 18-month Central Asian Dust Experiment we conducted continuous lidar measurements at the Physical Technical Institute of the Academy of Sciences of Tajikistan in Dushanbe between 2015 and 2016. Mineral dust plumes from various source regions have been observed and characterized in terms of their occurrence, and their optical and microphysical properties with the Raman lidar PollyXT. Currently a new container-based lidar system is constructed which will be installed for continuous long-term measurements in Dushanbe.

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